1. Field of the Invention
This invention relates to a process for refining metal ore containing at least one metal oxide. More particularly, it pertains to the direct conversion of an ore to a metal or an alloy by a continuous procedure involving two reducing steps in series.
2. Description of the Prior Art
The application of plasma technology to high temperature processes in the organic, inorganic, and extractive metallurgy areas has been widely researched. Previous investigations have included the plasma production of the acetylene and other hydrocarbons, nitrogen fixation, the production of oxides, carbides, and nitrides, the reduction of metal oxides and halides, benefication of complex minerals, and plasma remelting and refining. An example of a method and arc heater is shown in U.S. Pat. No. 3,765,870, entitled "Method of Direct Ore Reduction Using a Short Gap Arc Heater," by Maurice G. Fey and George A. Kemeny, issued Oct. 16, 1973. Other examples of similar processes are disclosed in that patent.
Despite extensive research, there are relatively few large scale commercial processes based on plasma technology. In general, those commercial processes have been confined to processes requiring temperatures not attainable by a conventional technique, to applications in which reduced capital requirements were of importance, or to processes where the plasma method resulted in a product with unique characteristics. In most cases, the plasma route has not been economically competitive because of higher energy costs. However, the situation is changing due to the shrinking supplies of light hydrocarbon fuels and to the development of a stable electric energy economy.
More specifically, heretofore the electrical requirements for an arc heater operated to reduce ores or oxides of most metals including iron, chromium, manganese and vanadium have not been economically feasible. Inasmuch as the power requirement of an arc heater for an ore reduction process are the primary operating costs, it is necessary that such costs be minimized wherever possible.